This invention relates generally to the handling and transfer of liquid manure and more particularly to a novel pump for agitating the liquid manure and when desired, for pumping it from a storage compartment or pit, without the use of valves.
In modern times it has become relatively common to dispose of manure in liquid form, from beef cattle feeding sheds, hog barns, dairy barns, etc. As generally pointed out in Nesseth U.S. Pat. No. 3,687,311, col. 5, line 40 et seq., the manure may be stored in a manure pit during the winter season and then pumped out and spread on the ground at a time when ground conditions prevent loss from runoff and prevent downstream pollution, probably especially by animal phosphates.
A manure pit, e.g. 4 to 8 feet deep, may be, and often is, located beneath a cattle feeding shed or barn, having a floor made up of concrete beams, e.g. 4 to 6 inches wide, with adjacent beams being located about one inch or more apart, to allow the manure to pass through to the pit and to permit washing down dirt with a hose. However, the manure pit or storage compartment, where desired, may be exterior to a barn or shed or beneath a feed lot.
When the time comes to remove the liquid manure from the pit, for spreading on the land, it is commonly pumped into a mobile tank which may be pulled by a tractor (or be mounted in a truck) and which is equipped with a spreader powered by a power takeoff (PTO) from the tractor. It is necessary to pump the manure from the normally depressed compartment or pit into the tank. However, before pumping the liquid manure from the pit into the tank, it is desirable first to agitate and mix the liquid manure in the pit so as to incorporate the solids and to develop a reasonably uniform slurry; because when the manure stands for weeks or months, its mineral content tends to settle to the bottom and fibrous material to come to the top, with liquid in between.
Pumps, introduced into the pit through a pumping port and supported on the adjacent surfaces around the porthole, have been in use which can be employed to agitate and mix and, when ready, then to pump the liquid manure through a discharge pipe to the tank or truck. These pumps commonly have two pipes connected to the impeller housing of the pump, one for agitation and the other for discharge or loading. Commonly gate valves are used to cut off passage through the discharge pipe when agitation is desired, and to cut off passage through the agitation pipe when discharge is desired. Both pipes are subject to the pressure of the pump and, if a valve does not close fully, material will continue to pass through it. Because of this, it often happens that after the valve is closed in the discharge pipe, and a tank that has been loaded has pulled away, liquid manure continues to leak through the valve into the discharge pipe and from it onto the ground in the loading area. This is obviously messy and annoying.
Because of these difficulties, one suggestion has been that two pumps should be used, one for agitation and another for discharge, thus to avoid difficulty with incomplete closing of the discharge valve. This suggestion is quite impractical because of the considerable increase in expense, as an extra pump of adequate capacity may cost another $2,000, or $3,000, or more. Obviously a dairy farmer or cattle feeder does not want to double his cost for pumps, or undergo the inconvenience of changing the power from one pump to the other with a change from loading to agitation, or vice versa.
These prior pumps have commonly been driven from the power takeoff of a farm tractor.
I am also aware that there are pumps of the centrifugal type which are valve-free, but none of these that I know of, with the possible exception of the Blum German DAS 1146299, will serve the dual function of alternately agitating and discharging liquid manure. The German DAS has never led to any usage in this country, to the best of my knowledge. The reason for such non-use seems apparent when one examines the structure disclosed in the Blum publication. As pointed out above, when manure stands in a pit, its mineral content tends to settle to the bottom and fibrous material to rise to the top, with liquid in between. It is undesirable in an effort to effect agitation or mixing, if not unworkable, to have an agitation nozzle, or the output of the pump, directed into the relatively solid mineral layer. Much more effective agitation is secured by directing the output from the pump, in a stream, above the mineral or relatively solid lower layer, whereupon the turbulence in the liquid material gradually draws solid material from the bottom layer into it and forms a relatively uniform slurry.
Further, the Blum publication proceeds on the theory that the pressure side of his pump or impeller, as the same is rotated, can be made to selectively register with any chosen sludge line or the feed line. Practically speaking, considering the irregularities to be expected in the floor surface of a liquid manure pit or the like, Blum provides no practical way to accomplish such registry. His sludge lines and discharge or feed pipe are not combined in a unitary structure with his pump, and his sludge lines are not adapted to be moved from pit to pit with his pump.